There is still a lot more room to run in the market, even though stocks have already rallied on optimism over tax reform, Raymond James policy analyst Ed Mills told CNBC on Monday.
Congress is expected to vote as early as Tuesday on the plan, which slashes the corporate rate to 21 percent from 35 percent. The odds of passage increased on Wednesday after Republican Sens. Mike Lee and Susan Collins said they would support the bill.
Mills said the impact of the final legislation is still unknown.
"A lot of investors, a lot of analysts, a lot of companies were caught flat-footed by this kind of sudden movement, especially in the Senate and now going to the conference report," he said in an interview with "Closing Bell."
Companies are not ready to give guidance and investors are "shocked" they are going to get as much of a benefit on the corporate side, he explained.
"People are still going through these details, still trying to figure out how much of a tax break is going to come for a lot of these corporations, and that's why I don't think a lot of this is yet fully priced in."
However, there will be relative winners and relative losers.
For example, banks will probably see at least an 18 percent upside to earnings once the legislation is fully priced in, he said.
U.S. stocks closed at an all-time high on Monday.